Changing interface between mock_factory and the composite HOD model.

Now, for the MC methods of the composite model, mock_factory will pass
the composite model the entire collection of halos. So now the composite model
will need to know what table columns to use when calling the component models.

Doing things this way simplifies the calls made to the model by the mock_factory,
and relegates the abstractions to hod_factory, where it belongs.
Finished modifying API of mock_factory to pass mc_occupation the full halo_table.

These recent commits required adding a lot of new code that still needs to be tested.
Surely still extremely buggy.
Filling out docstrings
Finished docstrings of halo_prof_components
Modified docstrings of hod_components
Starting to write docstring for hod_designer